Design Criteria for Betavoltaic Nuclear Batteries

Abstract

A betavoltaic device, the Betacel ® Model 400 L battery has been developed specifically for use in cardiac pacemakers. This paper discusses standards for design of environmentally qualified nuclear batteries and examines how effectively these are achieved in the betavoltaic device. The design of a nuclear battery involves safety, performance, and economics. The Nuclear Energy Agency and the U. S. Atomic Energy Commission have published protective standards and safety guidelines for nuclear-powered cardiac pacemakers. These documents outline tests to determine containment of radioisotope fuel under credible accident situations including impact, fire, cremation, and corrosion. These guidelines are considerably more severe than present industrial standards. In addition to safety, performance imposes important design constraints. These include size, weight, lifetime, and reliability specifications. Lower radiation dose rate requires more weight and bulk in shielding material within the battery. Reliability considerations require rigid quality control and many unit years of battery testing. Since the use of nuclear batteries is predicated on lifetimes substantially exceeding those of other systems, a lifetime of more than 5 years must be offered. Promethium betavoltaic nuclear batteries are currently limited in lifetime to about 10 years with state-of-the-art pacemakers. If needed, this lifetime can be expected to be extended with future developments. A design determined by safety and reliability criteria must also be economically competitive. A nuclear pacemaker system provides a low yearly cost to the patient by eliminating reimplantation costs of shorter-lived devices.